Magnetic separator

ABSTRACT

A magnetic separator is provided with two rotors arranged in spaced relation one above the other on a driven vertical shaft and each rotor is provided on its circumference with a large number of uniformly distributed plate sets, whereby the joints between the plate sets on one rotor are displaced with respect to the joints between the plate sets on the other rotor. The rotors are disposed between diametrically disposed fixed magnetic poles, the ends of which are pointed in circumferential direction of the rotors so that at the entry side of the poles the magnetic intensities increase gradually to their full strength, while at the exit sides of the poles the magnetic intensities decrease gradually to zero.

United States Patent [1 1 Vorster et a1.

[11} 3,869,379 [451 Mar. 4, 1975 MAGNETIC SEPARATOR [73] Assignee: Klockner-Humboldt-Deutz Aktiengesellschaft, Cologne, Germany [22] Filed: Nov. 2, 1973 [21] Appl. No.: 412,168

Related US. Application Data [63] Continuation of Ser. No. 129,681, March 31, 1971,

abandoned.

[52] US. Cl 209/222, 209/219, 209/223 R [51] Int. Cl. ..B03c1/14 [58] Field of Search 209/219, 222, 223, 224, 209/232, 216; 310/114 [56] References Cited UNITED STATES PATENTS 689,561 12/1901 McKenna 209/224 832,826 10/1906 Wait 209/219 1,965,441 7/1934 Tyclen i 209/219 2,074,085 3/1937 Frantz 209/222 2,078,513 4/1937 Stearns 209/219 3,021,007 2/1962 Jones 4. 209/223 3,045,822 7/1962 Cavanagh 209/219 3,326,574 6/1967 3,483,410 12/1969 Siegelman 310/114 3,535,572 10/1970 De Rugeris 310/114 FOREIGN PATENTS OR APPLICATIONS 252,034 5/1926 Great Britain 209/222 207,042 9/1966 Sweden 310/114 Primary E.\'aminerR0bert Halper Attorney, Agent, or FirmHi1l, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] 3 ABSTRACT A magnetic separator is provided with two rotors arranged in spaced relation one above the other on a driven vertical shaft and each rotor is provided on its circumference with a large number of uniformly dis tributed plate sets, whereby the joints between the plate sets on one rotor are displaced with respect to the joints between the plate sets on the other rotor. The rotors are disposed between diametrically disposed fixed magnetic poles, the ends of which are pointed in circumferential direction of the rotors so that at the entry side of the poles the magnetic intensities increase gradually to their full strength, while at the exit sides of the poles the magnetic intensities decrease gradually to zero.

3 Claims, 3 Drawing Figures l 10 ll ill, 11 1 l MAGNETIC SEPARATOR This is a continuation of application Ser. No. 129,681 now abandoned, filed Mar. 31, 1971.

The invention relates to a magnetic separator which is provided with at least one rotor rotatable about a vertical axis, whereby the circumference of this rotor has mounted thereon a large number of uniformly distributed plate sets. This rotor with its circumference comprising the mentioned large number of plate sets rotates between two diametrically opposed fixed pole shoes which partly surround the circumference of the rotor.

During the operation of such magnetic separators which operate with a strong magnetic field, it was discovered that in view of the arrangement of the plate sets on the circumference of the rotor the latter is forced to operate with a periodically varying rotative movement corresponding to the number of plate sets, even though the drive of the rotor takes place with a constant speed. This undesirable operation is caused by the entrance and the exit of the joints between each two adjacent plate sets into the magnetic field which causes an acceleration and a deceleration of the rotor. Owing to the strength of the magnetic field, these forced speed variations are of substantial intensity. This may cause dangerous torsion oscillations of the rotor shaft. Furthermore, the forced variation in speed is transmitted to the gearing arranged between the rotor and the drive rotor, so that due to the flank clearance of the gear wheels it is possible that impact-like stresses are transmitted to the teeth of the gear wheels.

It is an object of the invention to improve the rotative behavior of the rotor by means of improvements in construction.

In accordance with the invention, the desired object is attained in that with reference to the height of the circumferential surface, the ends of each pole shoe at the entrance side and/or at the exit side are reduced in their height. This arrangement has the result that the plate sets at the joint between two adjacent plate sets when entering into the magnetic field, are subjected gradually to the full strength of the magnetic intensity, while when leaving the magnetic field the platesets are subjected gradually to a reduction of the magnetic intensity in view of the reduction of the height of the pole shoes at the entrance and exit ends. Corresponding with the reduction of the height of the pole shoes the speed variations are reduced or entirely eliminated, independent whether the number of the plate sets is an even one or an odd one.

The invention provides that each end ofthe pole shoe is provided with at least one point which extends in the circumferential direction ofthe rotor. At the entry side of the pole shoe, viewed in the direction of the rotor, will then appear a constantly increasing field intensity corresponding to the gradually widening portion of the point until the full field intensity is reached, while at the exit side of the rotor a constant reduction of the field intensity down to zero takes place.

In addition to this change in the height of the pole shoe, it would also be possible to shape the pole shoe ends adjacent the circumference of the rotor in such a manner that Within the range of the entry and the exit end the pole shoe face does not extend concentrically with respect to the circumference of the rotor but has a slightly increased curvature and even may extend tangentially to the rotor so that the air gap between the pole shoe faces and the circumference of the rotor becomes gradually larger. This last feature will also have the effect that the increase of the field intensity up to the full field intensity and a decrease of the field intensity may be additionally accomplished.

According to a particular embodiment of the invention, the magnetic separator may be provided with at least two rotors which are arranged in spaced relations one above the other on a vertical shaft. Both rotors are provided each with the same number of plate sets, but the plate sets on one of the rotors are displaced with respect to the plate sets on the other rotor, namely in accordance with the invention in such a manner that the distance a of the displacement will be approximately equal to the length t of one plate set measured in circumferential direction and divided by twice the number x of rotors, so that a t/2x. With such a displacement of the plate sets on the rotors with respect to each other an optimum speed behavior will be obtained.

The invention will now be further described with reference to an example of a magnetic separator which is illustrated in the accompanying drawing.

IN THE DRAWING FIG. 1 illustrates diagrammatically a side elevation view of a magnetic separator provided with two rotors;

FIG. 2 illustrates a sectional view along the line llll of FIG. 1; and

FIG. 3 illustrates diagrammatically in an enlarged scale the portions of two rotors and pole shoes in which the plate sets are displaced with respect to one another.

Referring to the drawing, the FIGS. 1 and 2 illustrate by way of example a magnetic separator having a frame 1 in which a vertical shaft 2 is rotatably supported in vertically spaced bearings in order to be driven by a not-illustrated prime mover with a constant speed. Within the frame 1, the vertical shaft 2 has attached thereto two rotors 3, 3' in spaced relation one above the other. Each rotor has mounted on its circumference a plurality of uniformly distributed plate sets 4. Each plate set comprises a large number of vertically disposed thin metal plates 5 slightly spaced from each other and combined to form a set, whereby the surfaces of these plate sets extend in the circumferential direction of the rotor. The frame has two vertical members 6 and 7 on which the field coils 8 and 9 are secured. The core of each field coil at the end which faces the rotor changes into the shape of a pole shoe 10, whose pole face extends concentrically to the rotor. The entry side and the exit side 11, 12 of each pole shoe, with reference to the direction of the rotor, are beveled so that the pole shoe ends have, for instance, the shape of symmetrically arranged points as shown in the FIGS. 1 and 3. Of course, the points may have also another shape as long as the dimension in the height is decreased. The pitch of the bevel determines the increase and the decrease, respectively, of the magnetic field intensity between the pole faces and the rotors.

In the diagrammatic illustration of FIG. 3 which shows in an enlarged scale a side elevation view of portions of two rotors 3 and 3' arranged in spaced relation one above the other, the displaced arrangement of the plate sets 4 is illustrated. In this FIG. 3, the distance I indicates the length of one plate :set 4 measured along the rotor circumference. If both rotors were arranged in the same manner on the shaft 2, so that the joints between each two plate sets wouldl be in vertical align ment with each other then, when the rotors move in the magnetic field would still be very substantial, so that even in such an embodiment, namely when the rotors are arranged without any displacement of the plate sets, still a very noticeable acceleration and deceleration of the speed of the rotor-when moving through the two magnetic fields-would occur. If, however, the two rotors are displaced with respect to each other so that between the two superimposed plate sets 4 a distance a is produced, then the degree of acceleration and deceleration would be reduced. It was discovered that when the displacement a 1/2 twice the number of rotors, or a t/2x, namely here a A, an optimum arrangement is obtained in which the rotational speed of the rotor remains substantially uniform. Any remaining speed variations are in the first place the result of different magnetic properties of the materials of the rotors and the plate sets. These variations are, however, so small that practically a uniform speed of the rotor is obtained.

When the displacement of the plate sets in accordance with the invention is employed one may dispense with the points at the pole shoe ends even at strong magnetic intensities; or in other words, the ends of the pole shoes, when viewed in vertical direction, may extend parallel to the joints between the plate sets and still no disturbant speed variations will occur.

What we claim is:

l. in a magnetic separator, a stationary frame; a vertical drive shaft rotatably mounted in said frame; at least two rotors secured to said drive shaft one above the other, each of said rotors including a plurality of plate sets of substantially equal length in the circumferential direction of the rotor and uniformly distributed along the periphery thereof, the plate sets of one of said rotors being circumferentially offset in relation to the plate sets of the adjacent rotor by an amount substantially equal to the length of a plate set divided by twice the number of rotors; and pole shoes secured to said frame and having curved surfaces adjacent and substantially conforming in shape to the peripheries of said rotors.

2. The magnetic separator according to claim 1, in which the circumferential end portions of said pole shoes are of gradually decreasing width counted in the axial direction of the rotors.

3. The magnetic separator according to claim 2, in which said gradually narrowing end portions of the pole shoes terminate in a sharp edge. 

1. In a magnetic separator, a stationary frame; a vertical drive shaft rotatably mounted in said frame; at least two rotors secured to said drive shaft one above the other, each of said rotors including a plurality of plate sets of substantially equal length in the circumferential direction of the rotor and uniformly distributed along the periphery thereof, the plate sets of one of said rotors being circumferentially offset in relation to the plate sets of the adjacent rotor by an amount substantially equal to the length of a plate set divided by twice the number of rotors; and pole shoes secured to said frame and having curved surfaces adjacent and substantially conforming in shape to the peripheries of said rotors.
 2. The magnetic separator according to claim 1, in which the circumferential end portions of said pole shoes are of gradually decreasing width counted in the axial direction of the rotors.
 3. The magnetic separator according to claim 2, in which said gradually narrowing end portions of the pole shoes terminate in a sharp edge. 